Fungus Among Us: How Chytrid is Wiping Out Frogs Worldwide

 Fungus Among Us: How Chytrid is Wiping Out Frogs Worldwide

By: Zoe M.

National Geographic. (2025, January 13). Amphibian apocalypse: Frogs and salamanders face worst chytrid fungus crisis. Retrieved from https://www.nationalgeographic.com/animals/article/amphibian-apocalypse-frogs-salamanders-worst-chytrid-fungus

Imagine having only 21 days to live, your basic bodily functions failing because

of a ruthless pathogen. This invisible killer disrupts your ability to drink, breathe, exchange

ions, and regulate body temperature—vital processes you rely on to survive. For frogs,

this nightmare becomes reality when they’re exposed to chytrid fungus. Chytrid fungus,

is a mindless yet devastating pathogen, it has wreaked havoc on over 200 species of

amphibians, driving many populations to the brink of extinction—or beyond. In this blog

post, we’ll raise awareness about this deadly disease, exploring its impact

on amphibians and why it’s crucial to act before it’s too late.

MykoWeb. (n.d.). Amphibian killing chytrid fungus: A global crisis. Retrieved from https://www.mykoweb.com/articles/Amphibian-Killing-Chytrid.html

Chytrid fungus is a highly infectious disease devastating amphibian populations

worldwide. This disease is caused by two pathogenic fungi: Batrachochytrium

dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). While both are

forms of chytrid fungus, their differences lie in their preferred hosts and the symptoms

they cause.

Bd (Batrachochytrium dendrobatidis): Primarily affects frogs but can infect other

amphibians as well. Its hallmark is the thickening of keratinized layers in the skin,

disrupting vital processes like water absorption and electrolyte regulation.

Bsal (Batrachochytrium salamandrivorans): Targets salamanders and newts,

causing sores, deep skin lesions, severe weight loss, and systemic infections.

While both are significant threats, this blog post will focus on Bd (Batrachochytrium

dendrobatidis) because of its broad impact on both frogs and other amphibian species.

The first documentation of Bd (Batrachochytrium dendrobatidis) occurred in 1993 in

Australia, when a catastrophic wave of amphibians died-off, causing alarm among

scientists. During this time, several species were wiped out, prompting a global

response to understand and combat this emerging pathogen.

AmphibiaWeb. (n.d.). Chytridiomycosis: The amphibian chytrid fungus. Retrieved from https://amphibiaweb.org/chytrid/chytridiomycosis.html

Keith McDonald, a renowned frog ecologist and taxonomist, assembled an international

team of experts to study the crisis. Over several years of research, this team identified

the culprit as chytrid fungus. Molecular biologist Louise Goggin traced the organism’s

closest relative to Chytridium confervae, a fungus known for decomposing cellulose,

keratin, and chitin. This discovery highlighted Bd's (Batrachochytrium dendrobatidis)

ability to exploit amphibians' keratin-rich skin as a habitat, with devastating consequences.

Open Access Government. (2022, October 3). The amphibian chytrid fungus: An amphibian pandemic. Retrieved from https://www.openaccessgovernment.org/amphibian-chytrid-fungus-amphibian-pandemic/159742/

The life cycle of Batrachochytrium dendrobatidis (Bd) comprises of four main stages,

beginning with the zoospore phase. Zoospores are single-celled, motile organisms

equipped with one or more flagella, enabling them to swim through damp or aquatic

environments. These mobile cells move randomly until they encounter suitable

conditions for development. Upon attaching to a surface, the zoospores undergo a

critical transformation called encystation. This process shifts them from a motile

dispersal phase to a sessile growth form, marking the development of the sporangium.

The sporangium, a sac-like structure, plays a vital role in protecting and nurturing

developing zoospores. Once mature, the sporangium releases the zoospores into the

environment, restarting the cycle and facilitating the spread of this highly adaptive fungus.

AmphibiaWeb. (n.d.). Chytridiomycosis: The amphibian chytrid fungus. Retrieved from https://amphibiaweb.org/chytrid/chytridiomycosis.html

Bd thrives in environments where temperatures remain below 86°F and water is readily

available. This makes it well-suited to habitats such as damp soil, puddles, ponds,

lakes, and other aquatic ecosystems. Additionally, Bd favors slightly acidic to neutral pH

levels between 6 and 7. Environmental factors such as weather can significantly

influence its growth rate. For instance, cloudy days can lower daytime temperatures

while increasing nighttime warmth, creating optimal conditions for the fungus to develop

and spread more rapidly. These environmental preferences allow Bd to establish itself

and persist in various habitats, posing an ongoing threat to amphibian populations.

Recognizing the signs of chytrid fungus infection (Batrachochytrium dendrobatidis,

or Bd) in frogs is crucial for early intervention and prevention of widespread fatalities. In

the early stages of infection, one of the first symptoms is excessive shedding of skin.

Unlike normal shedding, the sloughed skin appears discolored, often taking on a tan or

light gray hue. As the disease progresses, additional symptoms may include reddening

of the skin, abnormal markings around the mouth, loss of appetite (anorexia), muscle

convulsions, and a noticeable reduction or complete absence of reflexes.

Reddit. (2023, August 9). An example of a fungal disease in a frog. Reddit: r/herpetology. Retrieved from https://www.reddit.com/r/herpetology/comments/1871prx/an_example_of_a_fungal_disease_in_a_frog/?rdt=56704

New Scientist. (2018, December 5). Nearly 100 species of frogs, toads, and salamanders wiped out by fungus. Retrieved from https://www.newscientist.com/article/2198070-nearly-100-species-of-frogs-toads-and-salamanders-wiped-out-by-fungus/

The most devastating effect of chytrid fungus is its impact on the frog's skin, a vital

organ for respiration and fluid balance. The fungus thickens and damages the

keratinized layers, eventually halting the exchange of oxygen and leading to suffocation.

This impairment also affects nutrient absorption and makes the frog vulnerable to

secondary skin infections. Without an available vaccine, the mortality rate remains

extremely high. Chytrid fungus is regarded as one of the most destructive pathogens in

wildlife history, responsible for significant biodiversity loss among amphibian populations

worldwide.

Amphibian Ark. (n.d.). Chytrid fungus and amphibian conservation. Retrieved from https://www.amphibianark.org/the-crisis/chytrid-fungus/

Biologists across the United States dedicate significant time and effort to protecting frog

populations from chytrid fungus. When a decline in amphibian numbers is observed,

water samples and frog swabs are collected to detect the presence of the fungus. If

chytrid fungus is confirmed, extensive measures are taken to prevent further spread and

mitigate its impact. Conservation efforts often include treatments, relocation, and

ongoing testing.

Washington University in St. Louis. (2013, September 19). Missouri ponds provide clue to killer frog disease. Retrieved from https://source.washu.edu/2013/09/missouri-ponds-provideclue-to-killer-frog-disease/

Treatments typically involve the use of antifungal medications and heat therapy, as

Batrachochytrium dendrobatidis is sensitive to elevated temperatures. Relocation

strategies focus on moving frogs to environments unsuitable for the fungus to survive,

thereby creating safer habitats. After these interventions, biologists perform follow-up

swab tests and water analyses to evaluate the success of their efforts in eradicating the

disease. Protecting amphibian biodiversity requires continuous monitoring and adaptive

management to combat this deadly pathogen effectively.

U.S. Fish and Wildlife Service. (2020, July 23). Fighting chytrid: Protecting amphibians from a deadly disease. Retrieved from https://www.fws.gov/story/2020-07/fighting-chytrid

U.S. Fish and Wildlife Service. (2020, July 23). Fighting chytrid: Protecting amphibians from a deadly disease. Retrieved from https://www.fws.gov/story/2020-07/fighting-chytrid

In conclusion, Chytrid fungus is a relentless threat to frogs and other amphibians

worldwide, but there are steps everyone can take to help. If you observe a frog in the

wild exhibiting signs of chytrid infection—such as abnormal shedding, red or discolored

skin, or lethargy—it's essential to act responsibly. Avoid handling the animal unless

absolutely necessary, as the fungus can spread easily through contact. Instead, report

your findings to local wildlife authorities, conservation organizations, or amphibian

monitoring programs. Many areas have dedicated amphibian conservation hotlines or

websites where you can share your observations.

Reptiles Magazine. (n.d.). Chytrid fungus and its impact on reptiles and amphibians. Retrieved from https://reptilesmagazine.com/tag/chytrid-fungus/

Additionally, always clean and disinfect any gear, such as boots and nets, after visiting

wetland areas to prevent the accidental spread of the fungus between habitats. Support

conservation initiatives by participating in citizen science projects, donating to

organizations focused on amphibian research, and spreading awareness about the

importance of protecting these vulnerable species. Together, with informed action and

dedicated effort, we can help safeguard the future of amphibians and the delicate

ecosystems they inhabit.

WHAT YOU CAN DO TO HELP 

Volunteer with the DNR:

 https://wiatri.net/inventory/FrogToadSurvey/

Donations to DNR Wildlife organizations: 

https://www.billerpayments.com/app/donationsui/?bsn=swidnrdonations#/donations/payment 

references

Department of Climate Change, Energy, the Environment and Water (DCCEEW). Chytrid disease and its impact on amphibians. Australian Government, 2020. https://www.dcceew.gov.au/sites/default/files/documents/c-disease_1.pdf.

Kahn, J. Frogs vs. chytrid fungus: Can a cure be found? Yale E360, 2019. https://e360.yale.edu/features/frogs-chytrid-fungus-cures.

Amphibian Ark. Chytrid fungus and amphibian conservation. Amphibian Ark, n.d. https://www.amphibianark.org/the-crisis/chytrid-fungus/.

Wisconsin Department of Natural Resources. Chytrid fungus in amphibians. Wisconsin Department of Natural Resources, n.d. https://dnr.wisconsin.gov/topic/wildlifehabitat/disease/Chytridfungusamph.

Cornell University, College of Veterinary Medicine. Chytridiomycosis: A deadly disease of amphibians. Cornell University, n.d. https://cwhl.vet.cornell.edu/system/files/public/cwhl-fact-sheetsbd.pdf.

Partners in Amphibian and Reptile Conservation (PARC). Bd: Chytridiomycosis fact sheet. PARC, 2022. https://parcplace.org/wp-content/uploads/2022/06/WFP-Fact-Sheet%E2%80%93Bd-Chytridiomycosis_3.pdf.

Cornell University, College of Veterinary Medicine. Chytridiomycosis. Cornell University, n.d. https://cwhl.vet.cornell.edu/disease/chytridiomycosis#:~:text=The%20disease%20has%20caused%20the,impacting%20frog%20species%20most%20severely.

Ohio Department of Natural Resources. Chytridiomycosis in amphibians. Ohio Department of Natural Resources, n.d. https://dam.assets.ohio.gov/image/upload/ohiodnr.gov/documents/wildlife/wildlife-management/Chytridiomycosis%20Amphibians.pdf.

University of California, Riverside. Chytrid fungus: An invasive species threat to amphibians. University of California, Riverside, n.d. https://cisr.ucr.edu/invasive-species/chytrid-fungus.

New South Wales Government. Frog chytrid fungus. NSW Environment and Heritage, n.d. https://www2.environment.nsw.gov.au/topics/animals-and-plants/native-animals/native-animal-facts/amphibians/frogs/threats-to-frogs/frog-chytrid-fungus#:~:text=Frogs%20only%20have%20keratin%20in,of%20their%20pond%20or%20stream.

U.S. Fish and Wildlife Service. Fighting chytrid: Protecting amphibians from a deadly disease. U.S. Fish and Wildlife Service, 2020. https://www.fws.gov/story/2020-07/fighting-chytrid.